The present invention relates to a merged MR (magnetoresistive) head having aligned magnetic pole tips, and a method of manufacturing the same.
In a magnetic disk drive, data is read and written by using a magnetic disk medium serving as a storage medium, and a magnetic head having a electromagnetic transducing element mounted on a floating slider floating and supported by the air bearing effect caused by high-speed rotation of the magnetic disk medium.
Recent demands for an internal storage unit or external storage unit of a personal computer and the like increase remarkably, and downsizing, a higher operation speed, and a higher recording density are strongly demanded in a magnetic disk drive.
For this reason, improvements for high performance have been made in the magnetic head serving as the major portion of the magnetic disk drive, the magnetic disk medium, positioning servo, signal processing, and the like. In particular, whereas the magnetic head conventionally performs write (recording) and read (play) with one electromagnetic transducing element, recently, use of a so-called write/read separation type merged MR head is becoming the main stream. The merged MR head uses a conventional inductive element for data write, and an MR element, the output of which does not depend on the speed relative to the magnetic disk medium and which utilizes the magnetoresistive effect, for data read. These two elements are integrated and mounted on one floating slider.
This merged MR head is manufactured by utilizing photolithography technique, and micropatterning technique similar to a semiconductor manufacturing process. For example, Japanese Patent Laid-Open No. 7-262519 (U.S. Pat. No. 5,438,747) discloses a merged MR head and a technique concerning a method of manufacturing the same.
FIGS. 5A to 5C show an example of a method of manufacturing a conventional merged MR head.
In order to decrease the side fringe magnetic field generated during recording, the conventional merged MR head has a recording gap layer having the same width as that of an upper magnetic pole and a sidewall aligned with the same plane where the side surface of the upper magnetic pole is present, and the pedestal of a lower magnetic pole/upper shield.
In the method of manufacturing a conventional merged MR head, the recording gap layer and the pedestal of the lower magnetic pole/upper shield are formed to have the same width as that of the upper magnetic pole. For this purpose, the recording gap layer is defined to have the same width as that of the upper magnetic pole by using ion milling and chemical etching. Subsequently, in accordance with ion milling, the pedestal of the lower magnetic pole/upper shield, having the same width as that of the upper magnetic pole and a side surface aligned with the same vertical plane where the side surface of the upper magnetic pole is present, is formed on the lower magnetic pole/upper shield by using the upper magnetic pole as the mask.
FIGS. 5A to 5C show the manufacturing method which uses ion milling when defining the recording gap layer to have the same width as that of the upper magnetic pole. A recording gap layer 23 is deposited on a lower magnetic pole/upper shield 22, and thereafter an upper magnetic pole 24 is formed on the recording gap layer 23 by electroplating using photoresist frame. A portion of the resultant structure other than the vicinity of the upper magnetic pole 24 is covered with a photoresist 26, and the recording gap layer 23 is defined by ion milling to have the same width as that of the upper magnetic pole 24.
Since the ion beam etching rate of the recording gap layer 23 is lower than the ion beam etching rate of the upper magnetic pole 24, when defining the recording gap layer 23 to have the same width as that of the upper magnetic pole 24, the thickness (height) of the upper magnetic pole 24 decreases largely. More specifically, FIG. 5A shows a state before the recording gap layer 23 is etched by ion milling, and FIG. 5B shows a state after the recording gap layer 23 is defined by ion milling by using the upper magnetic pole 24 as the mask (the broken line in FIG. 5B shows a portion to be etched by ion milling). In FIG. 5B, the thickness of the upper magnetic pole 24 is apparently smaller than that in FIG. 5A.
Subsequently, as shown in FIG. 5C, a pedestal 21 for the lower magnetic pole/upper shield 22 is formed on the lower magnetic pole/upper shield 22 in accordance with ion milling by using the upper magnetic pole 24 as the mask. The pedestal 21 has the same width as that of the upper magnetic pole 24 and is aligned with the same vertical plane where a sidewall or surface 24s of the upper magnetic pole 24 is present. In this case, the thickness of the upper magnetic pole 24 further decreases.
In other words, FIG. 5B shows a state before the pedestal 21, aligned with the same vertical plane where the side surface of the upper magnetic pole 24 is present, is defined on the lower magnetic pole/upper shield 22 in accordance with ion milling by using the upper magnetic pole 24 as the mask. FIG. 5C shows a state after the pedestal 21 is defined on the lower magnetic pole/upper shield 22 by using the upper magnetic pole 24 as the mask.
In FIG. 5C, the sidewall 24s of the upper magnetic pole 24, a sidewall 23s of the recording gap layer 23, and a sidewall 21s of the pedestal 21 are aligned within the same plane 25. Similarly, the respective sidewalls on the opposite side (the left-hand side in FIG. 5C) are aligned within the same plane.
FIGS. 6A to 6C show another example of a conventional merged MR head and a method of manufacturing the same.
A recording gap layer 33 is formed on a lower magnetic pole/upper shield 32, and thereafter an upper magnetic pole 34 is formed on the recording gap layer 33 by electroplating using photoresist frame. Subsequently, the recording gap layer 33 is defined to have the same width as that of the upper magnetic pole 34 by chemical etching.
In this case, since a chemical etching solution that etches not the upper magnetic pole 34 but the recording gap layer 33 can be selected, the thickness (height) of the upper magnetic pole 34 does not decrease. Subsequently, a pedestal 31 for the lower magnetic pole/upper shield 32 is formed on the lower magnetic pole/upper shield 32 in accordance with ion milling by using the upper magnetic pole 34 as the mask. The pedestal 31 has the same width as that of the upper magnetic pole 34 and is aligned with the same vertical plane as the side surface of the upper magnetic pole 34. In this case, the thickness of the upper magnetic pole 34 decreases (the broken line in FIG. 6B shows a portion to be etched by ion milling).
In the conventional merged MR head manufacturing methods described above, the thickness of the upper magnetic pole becomes undesirably smaller than the thickness necessary to generate a sufficiently strong magnetic field when the merged MR head records a signal on the magnetic recording medium.
The reason for this is as follows. When forming the recording gap layer and the pedestal of the lower magnetic pole/upper shield by ion milling in order to decrease the side fringe magnetic field, the upper magnetic pole serving as the mask during ion milling must be formed thicker in advance by an amount corresponding to the thickness decreased by ion milling. For this purpose, the photoresist required for forming the upper magnetic pole by electroplating using photoresist frame must be formed to have a thickness larger than that of the necessary upper magnetic pole and to have a desired width of the upper magnetic pole. However, as the width of the upper magnetic pole decreases to meet a demand for a higher density, such a photoresist becomes difficult to form.
In the former case, since the ion beam etching rate of the recording gap layer 23 is lower than the ion beam etching rate of the upper magnetic pole 24, when defining the recording gap layer 23 to have the same width as that of the upper magnetic pole 24, the thickness of the upper magnetic pole 24 decreases largely. In other words, the thickness of the upper magnetic pole 24 decreases largely in accordance with the procedure from FIG. 5A to FIG. 5B.
When forming the pedestal 21 for the lower magnetic pole/upper shield 22 by ion milling using the upper magnetic pole 24 as the mask, the thickness of the upper magnetic pole 24 further decreases. As a result, the thickness of the upper magnetic pole, which is necessary to generate a sufficiently strong magnetic field when recording a signal on the magnetic recording medium, may not be ensured.
In particular, when the width of the upper magnetic pole 24 becomes equal to or less than 2 .mu.m, the thickness of the upper magnetic pole 24 that can be formed by electroplating using photoresist frame is about 5 .mu.m at maximum. Therefore, when ion milling is performed for the recording gap layer 23 and the pedestal 21 portion for the lower magnetic pole/upper shield 22 by using the upper magnetic pole 24 as the mask, the thickness of the upper magnetic pole 24 becomes equal to or less than 3 .mu.m, which is smaller than the required thickness, 4 .mu.m.
In the latter case, the sidewall of the recording gap layer and the sidewall for the pedestal of the lower magnetic pole/upper shield cannot be formed on the same plane where the sidewall of the upper magnetic pole is present.
The reason for this is as follows. Assume that in order to avoid the problems of the former case, the recording gap layer is to be formed by chemical etching to have the same width as that of the upper magnetic pole and to have a sidewall within the same vertical plane where the sidewall of the upper magnetic pole is present. In this case, due to variations in chemical etching rate, it is difficult to stop etching as soon as the sidewall of the recording gap layer becomes located on the same plane where the sidewall of the upper magnetic pole is present.
More specifically, due to variations in etching rate of the recording gap layer 33 etched with a chemical etching solution, it is difficult to stop chemical etching as soon as the side surface of the recording gap layer 33 reaches the same plane 37a or 37b where a side surface or wall 34s of the upper magnetic pole 34 is present. As a result, as shown in FIG. 6B, the side surface of the recording gap layer 33 undesirably extends to the outer side of the same plane 37a where the sidewall 34s of the upper magnetic pole 34 is present, thus forming an etch residue 35, or the side surface of the recording gap layer 33 undesirably retreats backward to the inner side of the same plane 37b where the sidewall 34s of the upper magnetic pole 34 is present, thus causing an over-etching 36.
In the etch residue 35 portion, the over-extending recording gap layer 33 forms a mask. As shown in FIG. 6C, a sidewall 31s (on the left in FIG. 6C), on the opposite side, of the pedestal 31 for the lower magnetic pole/upper shield 32 is formed on a plane 38 on the outer side of the same plane 37a where the sidewall 34s of the upper magnetic pole 34 is present. Accordingly, the side fringe magnetic field is not decreased.
Furthermore, in a portion of the recording gap layer 33 where the over-etching 36 has occurred, the sidewall 31s of the pedestal 31 for the lower magnetic pole/upper shield 32 can be formed on the same planes 37a and 37b where the sidewall 34s of the upper magnetic pole 34 is present. However, the over-etching 36 portion of the recording gap layer 33 is not filled even in the later steps but is left as a hole. A foreign matter may enter through this hole to reach an element portion covered with a protection film, to corrode the element.